Changes in the chemical composition of the liquid fraction of cattle manure during storage

The article presents the results of laboratory studies on the chemical composition of the liquid fraction (LCF) of cattle manure obtained using the ST-1200 screw press separator. The aim of the study was to assess changes in the chemical composition of the liquid fraction of manure during storage. It was found that when storing LCF for two months at positive air temperatures without direct sunlight, the proportion of dry residue was 1,6–1,7%. During the first month of storage, the humidity decreased by 0,1%, and then remained stably at 98,3%. During storage, the pH of the substrate changed towards alkaline from 6,9 to 7,7 pH units. The mineralization processes of carbon-containing components of the suspension led to a decrease in the carbon concentration from 32 to 14% during the storage period, which had a positive effect on the content of total nitrogen, phosphorus, potassium and their available forms. During the first month of storage, an increase in the concentration of ammonium nitrogen in the solution to 662 mg / kg was noted, and then its decrease by 251 mg / kg during the second month of storage. For mobile phosphorus and potassium, their maximum concentrations were noted after two months of storage (77 and 1826 mg / kg, respectively). The imbalance of the liquid fraction of manure for phosphorus persisted for two months of storage. It was proven that the products of cattle manure processing in the form of a liquid fraction did not have excesses of permissible concentrations of heavy metals.